JPH0140059Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an optical current transformer using a magneto-optic effect element.

As is well known, various current transformers of this type using magneto-optic effect elements, such as Faraday elements, have been proposed. For example, to measure the current of a high-voltage conductor placed in a closed container filled with an insulating medium such as SF ₆ gas, a ring-shaped core made of a magnetic material is provided to surround the high-voltage conductor. A Faraday element is disposed in a gap provided in the core to apply an induced magnetic field to the core, an optical cable drawn from outside the sealed container is connected to the Faraday element, and light is supplied via a polarizer; Using the principle that the polarization angle of the Faraday element changes in proportion to the strength of the magnetic field, changes in the current flowing through the high-voltage conductor are converted into changes in the polarization angle of light, which are further changed into intensity of light via an analyzer. A structure has been proposed in which an optical cable is guided outside the sealed container and converted into an electrical signal by an optical-to-electrical converter within an electric station, for example.

However, when this optical current transformer is used for measurement by fitting its ring core to three-phase high-voltage conductors, the high-voltage The problem is that the magnetic field induced by the conductor is distorted at the gap part, the lines of magnetic force are unbalanced with respect to the central axis of the core, and the ring core receives rotational force with respect to the central axis due to interaction with the magnetic field of the other phase current. be. When the ring core is rotated by this rotational force, the position of the magneto-optic effect element disposed in the gap portion is shifted, and the relative position with the high voltage conductor of the other phase is also shifted. For this reason, the degree of influence by the magnetic field of the other phase changes, causing a change in the characteristics of the transformer output, and if there is an extreme deviation, there is a risk that the optical fiber connected to the element may be cut.

Therefore, an object of this invention is to provide an optical current transformer that can prevent rotation of the core with a simple configuration.

An embodiment of this invention is shown in FIGS. 1 to 8. That is, in this optical current transformation device, a Faraday effect element 3 is arranged in the gap part 2 (FIG. 4) of a ring core 1, and a non-magnetic fixed body 4 made of synthetic resin such as epoxy resin or polyurethane resin is integrally cast. As a result, the Faraday effect element 3 is embedded and fixed in the gap portion 2, and a projection portion 5 is formed in one direction in the axial direction of the ring core 1. On the other hand, the high voltage conductor 6 (Fig. 3) connected to the line is connected to the small diameter part 7.
and a large diameter portion 8, and a concave portion 10 is formed in the stepped surface 9 of the continuous portion. The ring core 1 is fitted into the small diameter portion 7 of the high voltage conductor 6, and the projection 5 is fitted into the recess 10, so that the end surface of the ring core 1 on the projection 5 side is supported by the stepped surface 9. Further, a screw is provided in the small diameter portion 7, and a screw ring 11 is screwed in to tighten the ring core 1 against the stepped surface 9.

In the figure, 12, 13 are optical connectors, 14,
15 is an optical fiber, 16 is a magnetic shield attached to the large diameter portion 8 and covers the ring core 1, and 17 is an insulating spacer conductor portion. In addition, in FIGS. 1 and 2, 18 is a gas-insulated opening/closing container, 19
is SF ₆ gas, for example, when applied in a 77kV three-phase bulk type gas insulated switchgear enclosure, each high voltage conductor 6, 6', 6'' of the three phases is equipped with an optical current transformer, and the 1, 1', and 1'' in FIG. 1 indicate each core. In Figure 2, the optical fiber 1 is connected from the light emitting circuit to
4 and a polarizer (not shown), a magnetic field proportional to the current flowing through the high voltage conductor 6 is applied to the Faraday effect element 3.
When supplied to the magnetic field, the polarization angle of the light changes in proportion to the strength of the magnetic field, and this light is guided by an optical fiber 15 via an analyzer (not shown), and the strength of the light is converted into an electrical signal. This signal is transmitted to the digital protection control system and predetermined control is performed.

With this configuration, the core 1 can be stopped from rotating by fitting the protrusion 5 provided on the fixed body 4 and the recess 10 provided on the high voltage conductor 6, and reliability can be improved. Furthermore, since the structure is simple and manufacturing is easy, the cost can be reduced. Furthermore, by pressing the core 1 with the screw ring 11, the outer diameter of the current transformer portion can be significantly reduced, which is advantageous when applied to the container 18.

As a modification of the fixing means for holding the core 1 against the stepped surface 9, as shown in FIG. In this case, the outer diameter of the transformer section becomes larger, but the other configurations and effects are the same as in the previous embodiment.

As described above, the optical current transformer of this invention forms a rotation-stopping recess in the continuous step surface of the large diameter part and the small diameter part of the conductor, and fixes the magneto-optic effect element in the gap part of the core. To provide an inexpensive and highly reliable optical current transformer that has a structure in which a protrusion that fits into the recess is provided on the body, so that the means for fixing the core can be easily made and rotation can be surely prevented. It has the effect of being able to

[Brief explanation of the drawing]

Fig. 1 is a sectional view of an embodiment of this invention, Fig. 2 is an axial sectional view thereof, and Fig. 3 is a partially detailed sectional view.
FIG. 4 is a front view of the core, FIG. 5 is a perspective view of the core including the Faraday element, FIG. 6 is a plan view thereof, FIG. 7 is a sectional view, and FIG. 8 is a sectional view showing a modification of the fixing means. It is a diagram. 1, 1', 1''...Core, 2...Gap part, 3
... Faraday effect element (electro-optic effect element),
4...Fixed body, 5...Protrusion, 6...High voltage conductor,
7...Small diameter part, 8...Large diameter part, 9...Step surface, 10
... recess, 11 ... screw ring (fixing means), 2
0... Presser ring (fixing means).

Claims (1)

[Claims for Utility Model Registration] (1) A conductor having a rotation stopper recess formed in a stepped portion where a large diameter portion and a small diameter portion are continuous, and a conductor that is fitted into the small diameter portion and has one end surface supported by the stepped portion. A ring core with a gap, a non-magnetic fixed body fixed to the gap part and provided with a protrusion that fits into the rotation stopper recess, a magneto-optic effect element embedded in this fixed body, and a magneto-optical effect element embedded in the fixed body, and a fixing means for fixing the clamp to the part. (2) The optical current transformer according to claim 1, wherein the fixing means is a screw ring screwed onto the small diameter portion of the conductor.